﻿<%@ WebHandler Language="C#" Class="ValidateCode" %>

using System; 
using System.Web;
using System.Web.SessionState;

public class ValidateCode : IHttpHandler, IRequiresSessionState
{
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        string checkCode = CreateRandomCode(4);
        context.Session["CheckCode"] = checkCode;
        CreateImage(checkCode);
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }
    private string CreateRandomCode(int codeCount)
    {
        string allChar = "0,1,2,3,4,5,6,7,8,9";
        string[] allCharArray = allChar.Split(',');
        string randomCode = "";
        int temp = -1;

        Random rand = new Random();
        for (int i = 0; i < codeCount; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
            }
            int t = rand.Next(9);
            if (temp == t)
            {
                return CreateRandomCode(codeCount);
            }
            temp = t;
            randomCode += allCharArray[t];
        }
        return randomCode;
    }

    private void CreateImage(string checkCode)
    {
        int iwidth = (int)(checkCode.Length * 11.5);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 18);
        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
        System.Drawing.Font f = new System.Drawing.Font("Lucida Handwriting", 10, System.Drawing.FontStyle.Bold);
        System.Drawing.Brush b = new System.Drawing.SolidBrush(System.Drawing.Color.White);
        //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
        g.Clear(System.Drawing.Color.Black);
        g.DrawString(checkCode, f, b, 1, 0);
        Random rand = new Random();
        for (int i = 0; i < 50; i++)
        {
            int red, green, blue;
            red = rand.Next(0, 255);
            green = rand.Next(0, 255);
            blue = rand.Next(0, 255);
            System.Drawing.Pen blackPen = new System.Drawing.Pen(System.Drawing.Color.FromArgb(red, green, blue), 0);
            int y = rand.Next(image.Height);
            int x = rand.Next(image.Width);
            //g.DrawLine(blackPen, 0, y, image.Width, y);
            g.DrawEllipse(blackPen, x, y, 1, 1);
        }

        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        HttpContext.Current.Response.ClearContent();
        HttpContext.Current.Response.ContentType = "image/Jpeg";
        HttpContext.Current.Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        image.Dispose();
    }

}